Ferromolybdenum is an iron molybdenum alloy normally having a molybdenum content of 60-80% by weight.
In most commercial applications ferromolybdenum is produced from molybdenum trioxide (MoO3) by a carbothermic reduction, an aluminothermic reduction, or a silicothermic reduction. The carbothermic process produces a high carbon ferromolybdenum, while the latter two produces a low carbon ferromolybdenum. Low carbon ferromolybdenum is more common than the high carbon alloy. Lumps of ferromolybdenum produced by these methods normally have densities around 9 g/cm3. Dissolving the lumps in the steel melt can be difficult due to the high melting point of the lumps, for instance the commercial grade FeMo70 has a melting point of 1950° C., and since the temperature of the steel melt is considerably lower, dissolution of the ferromolybdenum is mainly affected by diffusion processes, which prolong the dissolution time of the ferromolybdenum. Another factor is the high cost of raw materials in the aluminothermic reduction and silicothermic reductions. Furthermore, around 2% of the Mo can be lost in the slag in these processes.